Performance Boat Shop - My Boats engine is throttled all the way but does not get up to speed?

My Boats engine is throttled all the way but does not get up to speed?

I have a 1988 sportcraft 252 25ft I'm very new to boating. My boat speed gauge reads 45 mph but when the engine is throttled all the way it only gets up to 20 mph. I tried using the trim tabs but still does not go fast. I'm thinking about changing the spark plugs since the boat sat for 2 years before i bought it. My friends dad basically told me its to big of a boat to go fast but for having a v-8 it should haul. please help me

Public Comments

plugs wires oil change and tune the carb
yea that boat isn't going to go that fast...... as for spark plugs u should have changed them and all the fluids already......... btw go to a boat shop tell them what u have and ask them for a different prop to get u some more speed..... they will probably need to see what u have now.....
This boat should run about 30 mph, but if it's been sitting in the water for a few weeks or more the bottom (scum) will reduce it's top speed into the range you are getting. After checking to make sure your prop is "like new" , have the bottom pressure washed, an then take it out on a test run. New fuel, and tune-up are always a good idea. The speed gauges on boat's are meaningless, not like a car, they often are unreliable. Your boat was never a 40's plus boat. It's a low 30's boat. AND it will eat gas at that number. Good Luck!.
How much does the boat weigh? How many horsepower does the boat have? Have you cleaned the hull? You'd be amazed at how much any buildup on the hull can reduce the top speed. Do you have the correct prop on the boat? 20 is a bit slow. If the review in the link is your boat expect about 35 top speed, 30 cruise speed, typical for that type of boat. The 45 on the speedo means nothing.
OK, so by now you should already know a mechanic or a good boatyard you can trust, after all, sitting for 2 years must have necessitated many service outings to get it ready to go. If not, you need to find one right away. Not only for stuff like this, but if you have some sort of problem when you're not at a convenient place, to put it lightly, you need to have somebody to call. So you see where I'm goping with this, take it to your mechanic...
you probably have the wrong pitch or diameter prop on it
First off...boats are not like cars. A speedometer on a boat is fairly useless as there are so many variables. Boat engines are usually adjusted/ tuned by RPM and again many things can affect RPM. Boat wieght including gear and passengers,hull condition ie 2" of scum and PROP SELECTION! Which is probably the most important and hardest to adjust. Too light a pitch and your rpm go sky high but the boat goes slow ...too heavy a pitch and your boat engine never reaches planning speed. Also water speed indicators are highly unreliable. A gps is more accurate. Trim tabs can help the attitude and planing of a vessel but the speed adjustment is negligable. It is unlikely your boat ever went or was meant to go 45mph. Thats pretty fast on the water. A good mechanic will be able to fine tune your boat (not just engine)